DispatchingValueFormatter::getFormatter first searches a PT formatter, then a VT formatter. Currently, most of the mappings in WikibaseValueFormatterBuilders are VT, which means there is no error for type mismatches if the property has one of those types.
I have no clue if we should move most of the VT to PT mappings or change the logic or whatever. JS does this correctly.
Version: master
Severity: normal
Whiteboard: u=dev c=backend p=5 s=2014-05-20